A conventional deck lid of a vehicle is quite heavy. Usually, the deck lid is pivotally attached to a vehicle body using hinge strap assemblies and is typically spring biased towards an opened position. This biasing eases the burden on a vehicle operator in opening the deck lid.
A first or proximate end of a hinge strap is pivotally attached relative to the vehicle body. A second or distal end is affixed to the deck lid. With respect to hinge strap assemblies for deck lids, hinge boxes generally bolt beneath the back shelf and rear window of a vehicle. A pair of spaced apart ears on each hinge supports a pivot pin which extends through the proximate end of a respective hinge strap. These hinge boxes are relatively complex in configuration and rather expensive to manufacture.
Typically, biasing has been derived from one or more torque rods. Torque rods have been particularly widely used because they provide a biasing torque as a result of rotation of one end of the rod relative to the other. Thus, one end of a torque rod may be connected to the vehicle and the other end to a hinge strap attached between the vehicle and the deck lid to provide a biasing mechanism. When the deck lid closes, the end attached to the hinge strap moves through an arcing or curvilinear translational motion causing another portion of the torque rod to twist in torsion thereby storing energy. When the deck lid opens, the torque rod unwinds releasing energy and assisting in biasing the deck lid to an opened position.
Through appropriate selection of the torque rod diameter and length, a variety of deck lids of different weights and sizes may be appropriately biased with this method. Torque rods are also highly reliable, simple mechanical devices.
Several drawbacks exist with the above described hinge strap assemblies and their torque rods. First, torque rods which span transversely across the width of a vehicle occupy a significant amount of space in the trunk compartment. Second, hinge straps are usually designed to be placed apart from the side of the vehicle thereby intruding in the space within the interior portion of the trunk compartment to operate.
Another approach to biasing a deck lid pivotally attached to a vehicle is to use a linkage assembly powered by a gas strut. The linkage assembly typically includes a pair of links pivotally connected together at one end. One of the links is connected at its opposite end to the vehicle. The other one of the links is connected at its opposite end to the deck lid. The links fold when the deck lid is closed and unfold when the deck lid is opened. A gas strut operating with the linkage assembly biases the deck lid to the opened position. The gas strut applies pressure to the links to make them unfold and stay unfolded to support the deck lid when the deck lid is opened.
However, several drawbacks exist with using a gas strut. First gas struts are not reliable, especially in cold weather climates. Second, because of the unreliability, associated warranty costs increase.
There exists a need to use a linkage drive assembly without the disadvantages associated with a hinge strap assembly biased by a torque rod and a linkage assembly powered by a gas strut.